1. Field of Invention
This invention pertains to an apparatus for monitoring and controlling a production process. More specifically, this invention pertains to an apparatus connected to a production machine that acquires and analyzes data about the production process and adjusts the production machine to improve the efficiency of the production process.
2. Description of the Related Art
Most industrial processes used for production of discrete components or for continuous products involve a multitude of variables that affect the final product quality as well as the production efficiency or productivity. An example of a continuous production system is a paper mill producing rolls of paper of certain composition, thickness, and other characteristics to meet customer specifications. An example of a discrete component production system is a precision grinding machine making automotive cam shafts, crankshafts, or other components. Maximizing the product quality as well as productivity in a competitive environment requires a certain degree of control of the production system. This is generally only possible with the help of real time data of key process parameters and product quality attributes acquired using sensors installed on the production equipment. Although production equipment may possess the components needed to move the slides and spindles at numerically controlled rates or furnace controls to maintain a certain temperature, the sensors to provide the information about the system behavior are not always available and may have to be added. The availability of real time process data combined with the controllability of the production machines still requires the determination of a control strategy or methodology best suited for an effective process control under a given set of production conditions. To complicate matters further, certain conditions such as incoming stock on each part or the instantaneous sharpness of the tool may be dynamic variables and therefore are generally not known.
Some attempts have been made in the past towards fully automatic control of the process. However, this requires instrumenting the production machines to obtain real time information on the machine and spindle stiffness as well as the actual tool sharpness. Typical of the prior art are the devices of the following patents.
Patent NumberInventorIssue Date4,855,925BhatejaAug. 8, 19894,570,389Leitch, et al.Feb. 18, 19864,590,573HahnMay 20, 19866,098,452EnomotoAug. 8, 20006,128,547Tomoeda, et al.Oct. 3, 20006,234,869Kobayashi, et al.May 22, 2001
Leitch, et al., describe an automatic adaptive system to maintain a constant wheel sharpness without wheel breakdown. Hahn describes a computer controlled technique for rounding up holes in a grinding taking into account the spindle deflection. The inventions of Enomoto and Tomoeda automatically control the final workpiece diameter using a measuring head during grinding. Kobayashi describes measuring the ground workpiece diameter using a gauge head to reveal any abrupt changes or lack of changes in part size during grinding.
The inventions identified above are generally directed to attempts at the automatic control of a grinding operation based upon a specific, predetermined attribute of a the workpiece. However, none of these prior art patents disclose how to optimize and control the grinding process based upon broad criteria of workpiece quality attributes and system productivity, nor do they provide the flexibility to change the optimization criteria according to the specific process or the desires of the user. Finally, the prior art control systems require instrumented machines with sensors and gauge heads and, therefore, are generally not adaptable to existing grinding machines lacking the necessary instrumentation.